This invention relates generally to a pneumatic rotary tool, and more particularly to a pneumatic rotary tool capable of operating in forward and reverse directions.
Conventional pneumatic rotary tools, such as impact wrenches, comprise a housing and an air motor disposed in the housing. The air motor is powered by pressurized air received in the housing and drives rotation of a shaft supported by the housing. The shaft projects outward from the housing for engaging a fastener element, such as a nut or a bolt. The tools are typically provided with a control system for switching the mode of operation of the tool between a forward operating mode in which the fastener element is tightened and a reverse operating mode in which the fastener element is loosened. It is also common for the tool to include a regulating system for regulating the torque generated by the air motor and transmitted to the fastener element. For example, the impact wrench disclosed in U.S. Pat. No. 5,377,769 (Hasuo et al.) includes both an air supply valve having air supply regulating slots for regulating the flow of air to the motor and a changeover valve for controlling the forward and reverse operating modes of the wrench. Thus, there are two separate valves to control the direction of rotation and the torque.
The conventional pneumatic rotary tools described above are not as efficient as desired because the forward/reverse selector and the torque regulator function separately, requiring two distinct sets of valves and selectors. This results in increased manufacturing and operating costs and an increased risk of mechanical failure. Moreover, because two separate valves are used, the tool operator must typically release the grip of the tool to move the valves, or must use a second hand to move the valves, resulting in time consuming, inefficient operation.